Adam,
Are we talking a loaded overall length based on say 3.725" for the 3.85" CIP magazine? If the hard limit is the magazine length, and the Norma case is shorter than the PRC, more of the bullet is outside of the case, the neck and thus the internal combustion chamber. I'm fundamentally missing something here.
The same comparison is relevant to the .22 ARC vs .223 Rem. The constraint being 2.26" magazine length, and trying to put an 88gr bullet in a .223 leads to the snake in a turtle neck scenario. The .22 ARC pulls the case length back, makes the combustion chamber fatter, and less bullet protrudes below the neck/shoulder junction.
Sorry, I'm trying to wrap my head around this, something seems backwards.
Steve
"Steve,
you are actually looking at the right variables, but you are running into a paradox because you are forcing standard, restricted factory magazine constraints (3.725" CIP or 2.26" AR-15) as your fixed control baseline for an uncompromised ELR system.
If you hold a fixed, static Maximum Overall Length (COAL) to fit a restricted commercial magazine footprint, then yes, your math is correct: a shorter hull pushes more of the bullet nose forward and out of the neck. But that is a factory hunting rifle compromise, not an optimized extreme long-range blueprint.
When you build a dedicated one-mile machine from the inside of the bore outward, you headspace and throat the chamber for the projectile first, completely bypassing the magazine box constraint.
If you place the 300 Norma Mag and the 300 PRC side-by-side on a true control workbench- with both actions custom-throated to seat a massive, ultra-long 245-grain Berger EOL or 225-grain ELD-M exactly where it belongs (with the bullet's bearing-surface tail sitting perfectly at the base of the neck junction)--the physical blueprint changes completely.
Because the 300 PRC features a fundamentally longer 2.580-inch case body and an optimized long neck, it preserves 100% of your internal combustion chamber room. The bullet tail sits entirely forward of the powder column To achieve that exact same optimal throat layout with the shorter 2.492-inch Norma hull, your loaded COAL stretches out so incredibly far past factory specifications that it will no longer feed or function in a standard long-action receiver layout.
If you choke that 300 Norma down to actually fit into that standard 3.725" CIP magazine you mentioned, that massive 245-grain bullet tail is forced to plunge deep down past the neck-shoulder junction, acting like a steel piston that physically steals
12 to 14 grains of volume right
out of the center of your hull!
That is the Volumetric Density
trap. You end up with a smaller
net fuel tank, forcing you to stoke
the case with volatile, heavily
compressed, spike-prone
overpressures up near a
hazardous 68,000+ PSI boundary
just to try and match the PRC's
muzzle velocity runway.
It is the exact same story with the
.223 Rem Vs. .22 ARC
comparison. If you run a custom
single-feed barrel throated
specifically to maximize a heavy
95-grain Sierra MatchKing, the
.223 case runs completely out of
volumetric runway because the
bullet body chokes out its tiny 28-
grain fuel tank.
All things being
equal-same slow powder engine,
same barrel runway, same heavy
projectile-the tall, narrow
container preserves its net usable
volume, while the short case
forces bullet intrusion. You
cannot cheat the three-
dimensional space inside a
cylinder!
